Large-scale habitat recovery in the valley of the Kleine Nete

As a mandate from the Flemish Environmental Agency (VMM) in the frame of the LIFE+ project "Large-scale Habitat Restoration in the Kleine Netevallei", an ecohydrological study was made by AGT in the "Kleine Netevallei" area. The main aim of the study was to investigate which interventions in the water management contribute in maintenance and restoration of the groundwater-dependent terrestrial vegetation types. For this purpose, groundwater modelling and ecohydrological NICHE modelling were carried out.

The study area is characterized by several types of surface waters (i.e. canals, rivers, streams, canals, ponds) ) and shallow groundwater tables. The groundwater system consists of a phreatic, sand-dominated aquifer. Water sampling indicates that the groundwater system can be easily drained by the surface waters. However, the water level in the surface waters is strongly controlled and influenced by the tides.

During high water levels, drainage by surface waters is reduced leading to local waterlogging. Because of this sensitive interaction between the surface waters and the groundwater table, the modelling paid specific attention to this interaction and to the water balance in the unsaturated zone. Model calibration was done iteratively by using of SWAP simulations for the unsaturated zone, and MODFLOW simulations for the water flow in the saturated zone. The model was calibrated by using of measured water levels and validated with vegetation and flooding data. At the end, different scenarios were tested with different water level management and control structures in the surface water system.